This article aims to provide emergency responders with background information, general procedures, and response guidelines to operate in accidents involving multimodal containers. Part 1 deals with intermodal freight containers; here, we are discussing tank containers.
The use of portable tank containers (also known as “tank containers” or “iso-tanks”) has increased substantially in the past decade. Factors contributing to its popularity include improved safety, portability, reduced transportation costs, and the advantages of multimodal transportation systems. Like cargo tank cars and railway tank cars, different types of intermodal tanks are manufactured in accordance with many domestic and international standards. They are used to transport a wide variety of goods, including an increasing number of hazardous materials. It is estimated that by 2000, the total number of intermodal portable tank containers will exceed 90,000.
Multimodal portable tanks usually consist of a single, non-divided container fixed in a strong metal support frame that allows the device to be lifted by a suitably designed handling crane. The frame allows the portable tank to be fixed on ships and surface vehicles.
Tank container. The storage tank itself is usually a cylinder, with both ends closed by elliptical, hemispherical or flange-shaped cans. Although rare, rectangular tanks and tube tanks can also be found. Portable tanks are usually single undivided containers with a capacity not exceeding 6,340 gallons (24,000 liters). Multi-cabin intermodal tanks are rare; however, when discovered, each compartment was constructed as a separate tank. Intermodal portable tanks usually do not have internal baffles.
– Lining to protect the water tank from its contents. The lining can be rubber, glass or other coverings, which are applied to the inside of the water tank after construction.
– Refrigeration unit. Most storage tanks with refrigeration units are not equipped with their own power source; an external power source is required. Depending on the mode of transportation, options may include ship power systems, plug-ins for fixed installations, road chassis-mounted generators, truck generators, or generator containers.
– Heating device for handling very viscous products. Options include electric heating or steam heating. The electric heating coil unit is usually used where the product must be heated during transportation, and can be installed inside or outside the tank container. They use a three-phase power supply of 200-240 volts or 340-480 volts. Steam heating is provided by pumping steam through an external heater coil in the lower half of the tank.
-insulation. It can alleviate the influence of ambient temperature on the contents. Insulation materials include polyurethane foam, polystyrene foam, mineral wool and glass fiber. The insulation is usually three to four inches thick and is always covered with a waterproof jacket to make it weatherproof. The sheath is made of at least one millimeter thick metal or equivalent thickness of glass or fiber reinforced plastic. Remember, the water tank is fixed to the container frame; the insulation is not part of the tank.
-Electrical control. The electric control box is installed on the tank rack at the rear of the tank container (that is, the end where the discharge valve is located). The control box will contain a fuse or circuit breaker, a temperature controller, a main switch to isolate the tank container from the power source, and a method for selecting the correct circuit for the available main power source.
Building materials. Due to its strength and excellent performance at low temperatures, more than 90% of intermodal storage tanks are made of stainless steel. The rest is made of mild steel. Aluminum and magnesium alloy cans can also be found, but they cannot be used for maritime transport.
The thickness of the shell is measured based on the “equivalent thickness in low carbon steel” after forming. The shell thickness requirements can be summarized as follows:
If you see the outer ring on the intermodal tank, it is most likely a single-shell stainless steel tank. Most storage tanks are constructed in accordance with the American Society of Mechanical Engineers (ASME) pressure vessel standards. The welds are inspected by X-ray; the welds on the carbon steel tank are stress-relieved after welding.
Dimensions and supporting frame. The support frame of the tank container protects the tank body and provides the functions of stacking, lifting and fixing the container. It also supports walkways and ladders.
The most common size support frame for tank containers is length: 20 feet, width: 8 feet, and height: 8 to 912 feet. Very few tank containers used in the United States exceed 20 feet. The one exception is the half-height tank container of Sealand, which is 35 feet in length. However, 30-foot tanks may be found in other countries.
Two basic types of support frames can be found: “box type”, which encloses the tank in a cage frame with continuous side rails, and “beam type”, which uses a frame structure only at the end of the tank. “Beam type” relies on the inherent strength of the tank as a beam.
Portable tank containers are usually associated with the tank end equipped with a discharge valve, called the “back end of the tank”. When facing the rear end, determine the left and right sides.
Angle castings. Like freight containers, the supporting frame of tank containers is also constructed with corner fittings, usually called “corner castings.” They are used to fix storage tanks and use standard container handling equipment to lift them. The use of cast iron corner castings is prohibited. In the event of an accident, corner castings can be used to lift or move the tank, but the owner or manufacturer of the tank must be negotiated.
Many markings on tank containers can be used to gain knowledge about tank design and construction characteristics. These tags include the following:
Report mark and number. The tank container is registered with the French International Container Agency. They must be marked with a report mark and tank number. The first letter indicates the ownership of the tank; the tank number identifies the specific tank. These marks are usually located on the right side of the tank (when you face it from both sides) and on both ends (see below). They may be displayed on the tank itself or on the tank frame.
Specification mark. The specification mark indicates the standard for the construction of portable tanks. Tank containers must meet U.S. Department of Transportation (DOT) design, construction, and safety standards. These marks will be located on both sides of the tank, usually close to the tank’s report mark and number.
DOT exemption mark. Sometimes an exemption from DOT regulations is authorized. In these cases, the outside of each package/container must be clearly and permanently marked “DOT-E” followed by the designated exemption number (for example, DOT-E8623). On intermodal storage tanks, these marks must be two-inch letters.
AAR-600 mark. For interchange purposes in rail transportation, intermodal tank containers should meet the requirements of Section 600 “Tank Container Acceptability Specifications” of the American Association of Railroads (AAR) Tank Car Specifications. Tanks that meet these requirements will display the “AAR 600″ mark in 2-inch letters on both sides near the tank report mark and number. The “AAR 600″ mark indicates storage tanks that can be used for controlled materials; the “AAR-600NR” mark indicates storage tanks that cannot be used for controlled materials.
Country, size and type markings. The country code (two or three letters) indicates the country where the tank is registered. The water tank will display the size/type code (LR-2276 in the photo at the bottom of page 62).
The four-digit size/type code follows the country/region code. The first two numbers together represent the length and height of the container. The second pair of numbers is the model code, which indicates the pressure range of the tank.
Nameplate. Other technical, certification and operational data can be found on the nameplate permanently attached to the tank or frame.
The tube containing the tank transportation documents or material safety data sheet (MSDS) can also be found near the nameplate. These tubes are made of metal or plastic and are usually located at or near the rear end of the discharge valve.
Date of tank and valve test. If installed, the retest interval for storage tanks and safety valves shall not exceed five years. The retest and test deadline must be marked or templated on the tank or nameplate.
Signs and placards. Tank containers containing controlled materials must be marked and tagged. The four-digit identification number must be displayed. For domestic transportation within the United States, DOT regulations require that the correct shipping name be printed in 2 inch letters on two opposite sides of the container shell. In international transportation, foreign placards other than the placards required by the United States are sometimes found. European goods may carry ADR/RID marks.
Some specific conditions that responders should pay attention to when OEM international shipments are as follows:
– Storage tanks containing regulated commodities must display corresponding DOT signs to correspond to the classification of the commodities. In addition to the required DOT label, you should find any additional labels authorized by the International Maritime Dangerous Goods Regulations (IMDG) [see 49 CFR 172.502(c)(1)].
– The required sign must comply with the DOT sign design specification. For example, it is illegal to use flammable liquid placards instead of flammable liquid placards, even if their size, color, and intent are the same.
Tank containers are classified according to the specifications of portable tanks and their accessories. The type of tank container determines which products can be transported. The general categories of tank containers include non-pressurized, pressurized and dedicated. The Multimodal Tank Table in 49 CFR Part 173 provides a list of hazardous materials approved by the DOT for transportation in portable tank containers.
The three most widely used specification tank containers that allow the transportation of hazardous materials in North America are IM-101, IM-102, and Spec. 51 containers. These portable tanks generally comply with the International Shipping Design Code established by the International Maritime Organization (IMO) for IMO Type 1, IMO Type 2 and IMO Type 5 tanks.
Although classified as non-pressurized vessels, the working pressure of these vessels can be as high as 100 psig. Non-pressure tank containers account for more than 90% of the total number of tank containers; the most common are IM-101 and IM-102 portable tank containers. The only clue to distinguish IM-101 and IM-102 containers is to physically check the nameplate or container markings.
Non-pressure tank containers can transport liquid and solid materials up to 100 psig maximum allowable working pressure (MAWP). The tank is tested to at least 1.5 times the MAWP.
IM-101 portable tank (International IMO Type 1). These tanks can withstand MAWP from 25.4 psig (1.75 bar) to 100 psig (6.8 bar). The DOT specifications for the design and construction of IM-101 tanks can be cited in 49 CFR 178.270 and 178.271.1. No ASME certification or seal is required.
IM-101 tanks are used to transport hazardous and non-hazardous materials, including toxins, corrosive substances, and flammable materials with a flash point below 327F (07C). The capacity is usually in the range of 5,000 to 6,300 gallons.
IM-102 portable tank (International IMO 2 type). These tanks can withstand low MAWP, ranging from 14.5 psig (1.0 bar) to 24.4 psig (1.75 bar). The DOT specifications related to the design and construction of IM-102 tanks can be cited in 49 CFR 178.270 and 178.272. No ASME certification or seal is required.
The IM-102 tank can transport materials such as whiskey, alcohol, certain corrosives, insecticides, insecticides, resins, industrial solvents, and flammable materials with a flash point ranging from 327F (07C) to 1407F (607C). These containers are also commonly used to transport unregulated materials, such as food-grade goods. The capacity is usually in the range of 5,000 to 6,300 gallons.
-Nameplate. Each tank must have a corrosion-resistant nameplate that is permanently attached to the portable tank in an easy-to-check position. If the information is provided in metric form, the respondent may encounter some initial difficulties when converting. The following information is required:
– Tank container accessories. The following accessories can be found on IM-101 and IM-102 tank containers to make them safe and practical. Although many of these fittings are similar to those found on cargo tankers, container fittings and threads are usually British Standard Pipe (BSP) or metric.
Access to the top fittings is usually through ladders and walkways installed on the container. Tank container ladders may become loose or weakened. In an emergency, emergency responders should consider using portable ladders to access the top of the container. Don’t walk on the tank shell.
* Overflow box. On most non-pressure storage tanks, there is an overflow prevention box around the top fittings to protect the tank shell from product overflow. The spilled material and rainwater in the overflow tank are drained to the ground through one or more small open pipes.
* Manhole, cover and oil dipstick. An 18 to 22 inch manhole is located in the center of the top of the tank. It is closed by hinges or bolt covers equipped with six or eight large wing nuts. Replacement gaskets are used for manholes; neoprene (food quality) is standard. Other gasket materials may include Viton© and Teflon©.
The dipstick may be located in the manhole or in the spill tank. It is used in conjunction with a calibration chart (also called a “strapping chart”) to measure the amount of product in the tank. The tank must be loaded to at least 80% of its capacity to avoid shaking. For liquids, a downtime of at least 2% of the total tank capacity must be provided in rail transportation.
* Top-mounted valve. The top loading valve is connected to a movable discharge pipe (for example, dip pipe, dip pipe, or siphon), which enters the storage tank. They can range from 112 to 4 inches in diameter, although they are usually 3-inch diameter ball valves or butterfly valves with four-bolt flanges.
* Bottom outlet valve. Their diameter ranges from 112 to 4 inches. When tank containers are used to transport hazardous materials, two externally operated bottom outlet valves are required. The typical design is for three-inch inner bottom valves, three-inch outer butterfly valves, and three-inch BSP threaded nuts. They are connected in series by replaceable gaskets. Some containers may also have electronic sensor connections adjacent or as part of the bottom outlet valve to provide product identification and product spill protection. This is similar to the sensor connection common on gasoline tank trucks to prevent the product on the loading rack from overflowing.
A liquid-tight closure on the external valve is also required. It can be a blind flange, a screw cap, or a cam lock cap connected to an external valve. Blind flanges are required for international transportation. AAR 600-12 requires a forced lock on the external foot valve to lock in the closed position.
Emergency response experience shows that, compared with the valve itself, most of the leakage occurs at the blind flange. The flange leakage can be easily controlled by tightening the flange bolts.
* Airline contact. Pneumatic connections can be used to relieve pressure, return steam and cover the contents with inert gas. It is usually a 112-inch line. In some cases, a 112-inch ball valve and pressure gauge may be found. This connection can be found on the top of the tank, usually in the overflow box.
Post time: Nov-10-2021
